The present invention relates to converters, power supplies, more particularly, to single, or multi stage, AC/DC or DC/DC isolated and non-isolated push-pull converters including but not limited to, forward, flyback, buck, boost, push pull, and resonant mode converters, and power supplies, having individual or distributed NSME with high speed FET switching and efficient flyback management and or having input PFC (power factor correction) and input protection from lightning transients. The invention also allows the magnetic element(s) be distributed to accommodate packaging restrictions, multiple secondary windings, or operation at very high winding voltages.
There are several basic topologies commonly used to implement switching converters.
A DC-DC converter is a device that converts a DC voltage at one level to a DC voltage at another level. The converter typically includes a magnetic element having primary and secondary windings wound around it to form a transformer. By opening and closing the primary circuit at appropriate intervals control over the energy transfer between the windings occurs. The magnetic element provides an alternating voltage and current whose amplitude can be adjusted by changing the number and ratio of turns in each set of the windings. The magnetic element provides galvanic isolation between the input and the output of the converter.
One of the topologies is the push-pull converter. The output signal is the output of an IC network that switches the transistors alternately xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d. High frequency square waves on the transistor output drive the magnetic element into AC (alternating current) bias. The isolated secondary outputs a wave that is rectified to produce DC (direct current). The push-pull converters generally have more components as compared to other topologies. The push-pull approach makes efficient use of the magnetic element by producing AC bias, but suffers from high parts count, thermal derating, oversized magnetics, and elaborate core reset schemes. The destructive fly-back voltages occurring across the switches are controlled through the use of dissipative snubber networks positioned across the primary switches. Another of the topologies is the forward converter. When the primary of the forward converter is energized, energy is immediately transferred to the secondary winding. In addition to the aforementioned issues the forward converter suffers from inefficient (dc bias) use of the magnetic element. The prior art power supplies use high permeability gapped ferrite magnetic elements. These are well known in the art and are widely used. The magnetics of the prior art power supplies are generally designed for twice the required power rating and require complex methods to reset and cool the magnetic elements resulting in increased costs and limited operating temperatures. This is because high permeability magnetic elements saturate during operation producing heat in the core, which increases permeability and lowers the saturation threshold. This produces runaway heating, current spikes and/or large leakage currents in the air gap, reduced efficiency, and ultimately less power at higher temperatures and/or high load. The overall effects are, lower efficiency, lower power density, and forced air/heatsink dependant supplies that require over-rated ferrite magnetic elements for a given output over time, temperature, and loading.
The combined improvements of the invention translate to higher system efficiencies, higher power densities, lower operating temperatures, and, improved thermal tolerance thereby reducing or eliminating the need for forced air cooling per unit output. The non-saturating magnetic properties are relatively insensitive to temperature (see FIG. 17), thus allowing the converter to operate over a greater temperature range. In practice, the operating temperature for the NSME is limited to 200 C. by wire/core insulation; the non-saturating magnetic material remains operable to near its Curie temperature of 500 C. What are needed are converters having circuit strategies that make advantageous use of individual and distributed NSME.
What are needed are converters having buffer circuits that provide fast, low impedance critically damped switching of the main FET""s.
What are needed are converters that incorporate efficient multiple xe2x80x9cstress-lessxe2x80x9d flyback management techniques to rectify and critically damp excessive node voltages across converter switches.
What are needed are converters having flux feedback frequency modulation.
What are needed are converters that correct AC power factor.
What is needed are converters that meet or exceed class B conducted EMI requirements.
What are needed are converters tolerant of lightning and harsh thermal environments. The present invention addresses these and more.
The main aspect of the present invention is to implement converters having circuit strategies that make advantageous use of individual and distributed NSME for the achievement of the key performance enhancements disclosed herein.
Another aspect of the present invention is to provide unique resonant tank circuit converter strategies with individual and distributed NSME that make use of higher primary circuit voltage excursions in the production of high frequency/high density magnetic flux.
Another aspect of the present invention is a high energy density single stage frequency controlled resonant tank converter topology enabled by the use of individual and distributed NSME. Another aspect of the present invention is to provide a converter design that utilizes a FET drive technique consisting of an ultra fast, low RDS on N-channel FET for charging the main FET gate and an ultra fast P-channel transistor for discharging the main FET gate.
Another aspect of the present invention is to provide converters that incorporate efficient multiple xe2x80x9cstress-lessxe2x80x9d flyback management techniques to rectify and critically damp excessive node voltages across converter switches.
Another aspect of the present invention is to provide a converter having core (flux) synchronized zero crossing frequency modulation.
Another aspect of the present invention is to present a high power factor to the AC line.
Another aspect of the present invention is to provide protection from high voltage (input line) transients.
Another aspect of the present invention is to combine distributed magnetics advantageously with the other converter aspects.
Another aspect of the present invention is active ripple rejection provided by several high-gain high-speed isolated control and feedback systems.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.